AP Bio 1.1, 1.2

Adhesion

The attractive force between water molecules and other polar substances, allowing water to stick to different surfaces.

Cohesion

The attractive force between water molecules that causes them to stick together, resulting from hydrogen bonding.

Evaporative cooling

The process by which the evaporation of water removes heat from an organism or environment.

Heat of vaporization

The energy required to convert a liquid to a gas, enabling water to remove heat from organisms through evaporative cooling.

Homeostasis

The maintenance of stable internal environmental conditions in an organism despite external and internal changes.

Hydrogen bonds

Weak attractive forces between a hydrogen atom bonded to an electronegative atom and another electronegative atom, occurring between or within biological molecules. it creates cohesion, adhesion and surface tension.

Polar covalent bonds

Chemical bonds between atoms where electrons are unequally shared, resulting in partial positive and negative charges.

Polarity

The unequal distribution of electrical charge in a molecule, resulting in one end being partially positive and the other partially negative.

Specific heat capacity

The amount of energy required to raise the temperature of a substance by one degree, allowing water to resist rapid temperature changes. ex: water needs a large amount of heat energy to raise its temperature, and it releases much heat when cooling down.

Surface tension

The property of water that allows its surface to resist breaking, resulting from hydrogen bonding between adjacent water molecules.

Hydrophillic

Substances that attract and dissolve in water (water‑loving). Usually polar / charged. eg salt

Hydrophobic

Substances that repel and do not dissolve in water (water‑fearing). Usually non‑polar. eg oil

“like attract like”

Polar substances attract polar substances, while non polar attracts non polar only; polar and non polar don’t attract each other. for ex: oil(nonpolar) and water(polar).

transpiration

The loss of water vapour from plant leaves through stomata.

aqueous

Describing a substance dissolved in water.

Expansion upon freezing

The unusual property of water where it increases in volume (expands) when it freezes from liquid water into solid ice.

Versatile solvent

Water is called a versatile solvent because it can dissolve a wide range of different substances.

Properties of water

1. Cohesion Behavior: Cohesion, Adhesion, transpiration

2. Moderation of temperature: Thermal energy (heat), temperature, High specific heat, evaporative cooling.

3. Expansion upon freezing: insulation by ice

4. Water = Solvent of life: Solution, Solvent, Solute.

pH < 7

Acidic

pH = 7

Neutral

pH > 7

Basic (alkaline)

Growth

Increase in size, mass, or cell number of an organism over time.

Nutrition

Obtaining and processing food molecules for energy and building materials.

Respiration

Chemical process releasing energy from organic molecules; produces ATP for cell work.

Solvent

Substance that dissolves other substances (water = universal/versatile solvent).

Reproduction

Process producing new individuals, passing genetic material to offspring (sexual / asexual).

Regulation (Homeostasis)

Maintaining stable internal conditions despite changes in the external environment.

Excretion

Removal of metabolic waste products produced inside cells.

Synthesis

Building larger complex molecules from smaller simpler subunits (anabolism).

Transport

Movement of substances (nutrients, wastes, gases) inside an organism or cell.

Organic compound

Compounds that contain carbon‑hydrogen (C‑H) bonds, usually associated with living things.

Hydrocarbons

Molecules made only of carbon and hydrogen. Non‑polar, hydrophobic.

Tetravalent

Carbon property: carbon has 4 valence electrons, can form 4 covalent bonds with other atoms.

Isomers

Molecules with the same molecular formula but different structural arrangements → different properties.

Structural isomers

Same chemical formula; atoms bonded together in different order / different covalent skeleton.

Cis‑trans isomers (geometric isomers)

Differ in arrangement around a carbon‑carbon double bond. cis: similar groups on same side of double bond; trans: similar groups on opposite sides.

Enantiomers

Mirror‑image isomers; cannot be superimposed (chiral carbon required). Often one form is biologically active.

Functional group

Specific groups of atoms attached to carbon skeleton; determine chemical properties / reactivity of organic molecules (e.g., ‑OH, ‑COOH, ‑NH₂, ‑PO₄).

Carbohydrates

Organic molecules: C, H, O (H:O = 2:1). Use: energy, structure. Monomer = monosaccharide.

Proteins

Made of C, H, O, N (sometimes S). Monomer = amino acid. Wide functions: enzymes, structure, transport, defence.

Lipids

Mostly C, H, small O. Hydrophobic / non‑polar. Includes fats, phospholipids, steroids. Energy storage, membranes, hormones.

Nucleic acids

C, H, O, N, P. Monomer = nucleotide. DNA & RNA; store & transfer genetic information.

Carbon (C)

Backbone of all organic molecules; tetravalent, builds diverse skeletons.

Hydrogen (H)

Forms bonds with carbon; involved in hydrogen bonding.

Oxygen (O)

Found in carbohydrates, proteins, lipids, nucleic acids; creates polar groups.

Nitrogen (N)

Present in proteins (amino‑NH₂) and nucleic‑acid bases.

Phosphorus (P)

Found in nucleic acids, ATP, phospholipids.

The four main organic molecules

Carbohydrates, lipids, proteins, nucleic acids.

Acid

A substance that donates/releases H⁺ ions when dissolved in water. Increases hydrogen ion concentration ([H^+]); pH < 7.

Base

A substance that releases OH⁻ ions (or accepts H⁺ ions) in water. Increases hydroxide ion concentration ([OH^−]); reduces ([H^+]); pH > 7.

H⁺ ions (hydrogen ions)

Positively charged hydrogen ions; the concentration of H⁺ determines pH. More H⁺ → more acidic, lower pH.

OH⁻ ions (hydroxide ions)

Negatively charged hydroxide ions. More OH⁻ → more basic (alkaline), higher pH.

Universal solvent

Another name for water, which dissolves a wide variety of ionic and polar substances due to its polarity.

Xylen

ascular plant tissue that transports water and dissolved minerals upward from roots to leaves, also gives structural support to the plantThe Univer...

Solution

A homogeneous (uniform) mixture of two or more substances. One substance dissolves into another.